The RMA then could leverage that money in a couple of ways, officials said — for instance, by issuing toll bonds — to finish out the total project cost.

The proposal was floated at the RMA's board meeting Thursday, but board members did not vote on the issue. They indicated they would very soon.

The plan makes sense, said RMA Executive Director Terry Brechtel, based on traffic patterns, high congestion and available funding that, for a number of reasons, make it easier to finance toll road construction on both corridors instead of just one.

“I can't look at this as little individual fixes,” Brechtel said after the meeting. There are urgent congestion problems in the area, she said, and “I can't fix part of it.”

The sections of U.S. 281 and Loop 1604 proposed for toll projects are best suited for tolling because they have some of the most traffic in the area, and populations around them are expected to significantly grow, according to a study commissioned by the RMA.

The RMA is specifically looking at adding toll lanes to Loop 1604 from Bandera Road to U.S. 281, and on U.S. 281 from Loop 1604 to the county line, so the toll projects on each corridor connect.

It isn't clear, though, how those toll lanes would tie into another plan to add nontoll lanes to parts of U.S. 281 from 1604 to Stone Oak, or to the nontoll interchange now being built.

Increasingly, the possible solution to the city's congestion woes is starting to look like a complicated jigsaw puzzle of funding sources.

Some transportation agencies have said they must turn to tolling as a way to expand roads and add more traffic lanes because state and federal funding is limited.

But the money the RMA had to launch some of its toll projects has shrunk, too.

A year ago, the agency still had $216 million in leveraging dollars, money funneled to the agency from the state. But $86 million of that was recently put toward the plan to add a mix of free and toll lanes on U.S. 281 and on another part of Loop 1604, from Bandera Road to Potranco.

That's left the RMA with $130 million to use.

After discussing the plan with RMA leadership on Wednesday, Bexar County Judge Nelson Wolff said he was interested in knowing more about the plan's financial viability, but he said the idea was “worth pursuing.”

“It may make sense doing this,” he said.

Whatever the RMA pursues in the coming months could affect Bexar County: in June, Commissioners Court launched a plan to take over the agency's operations. The county has slowed that process, waiting to pursue legislation that would give it the RMA's powers and authority.

If that happens, Bexar County could assume control over any toll projects. It also could mean taking on debts.

Also on Thursday, the San Antonio City Council granted the RMA an indefinite extension on a $500,000 loan the agency borrowed in 2005.

Under the new agreement, the RMA — or its future parent agency — can pay back the loan whenever it can afford to.